Thin magnetizable film having striped domains has been used as magneto-optic diffraction gratings. Variation of the separation and width of striped domains of thin-film magnetizable gratings and the resultant angle of diffraction by the Kerr and Faraday effects through control of an fixed magnetic field is also known. The use of such gratings as optical modulators, switches and multiplexers in integrated optical devices has also been disclosed. Such uses are limited, however, to controlling the angle of diffraction of incident light by setting an applied magnetic field at a fixed value using fixed wavelength signals.
Real time spectral analysis is presently carried out in a number of ways, one of which is to collimate the unknown spectral distribution, transmit it through or reflect it from a mechanical diffraction grating to separate the spectral components according to a first order angle and detect the relative spectral intensities via a charge coupled device (CCD) photodetector array. Another method which is used in chemical spectroscopic analysis replaces the expensive CCD photodetector array with a simple photodetector and rotates the diffraction grating mechanically with the spectral component incident on the detector. The detected light is thereby directly related to the amount of rotation of the grating.
The expense of CCD-based systems, and the limited speed and mechanical nature of such chemical spectroscopy systems leaves a need for a nonmechanical electrically controllable spectral analyzer which serves as a detector for one or a multiplexed number of wavelength-encoded sensors. Wavelength-encoded optical sensors which rely upon mechanical diffraction gratings also have inherent disadvantages of size and weight and typically require accompanying optics which make practical applications difficult.